The present invention generally relates to semiconductor packaging, and in particular to a device useful in changing dambar punches.
ICs in die form are rather delicate. Usually, they are packaged by encapsulation in plastic with external metal leads. The process begins by placing the IC die on a dap of a metal lead frame. FIG. 1 illustrates a typical leadframe 100 with daps 110. The IC die is connected to leads 120, with soldered wires for example. At this stage of the process, leads 120 are connected by dambars 130. To encapsulate the die, two halves of a plastic mold are placed around the IC die and the mold is filled with a liquid plastic precursor. As illustrated in FIG. 2, dambars 130 retain plastic 140 within mold 150 while plastic 140 is curing. That portion of plastic 160 that solidifies between leads 120 next to the dambars 130 is referred to as xe2x80x9cflash.xe2x80x9d
After the plastic solidifies, the mold is taken away and the dambars and flash are removed. The dambars and flash may be removed together or in separate steps. In either case, the dambars are usually removed by dambar punches. All the dambars may be punched out at once, or they may be punched out in several groups. Typically, half the dambars are removed in one punch step and the remaining dambars are removed in another. Dambar punches are produced for specific IC packages since lead count, lead pitches, and package sizes vary among different IC packages.
Dambar punches wear through use and must be replaced periodically. As pitch sizes get smaller, so do the dambar punches, making them ever smaller and more susceptible to wear. Worn punches cause dambar burr on the leads. Replacement of dambar punches is a time consuming process. Many dambar punches are required for high lead count packages and the dambar punches are small and difficult to handle. The dambar punches are ordinarily installed by hand, one at a time, using tweezers. In a typical situation, replacing a set of dambar punches in this manner takes half an hour. During this time, expensive automated IC packaging equipment remains idle, significantly impacting the manufacturing cost of IC packages. There is an unsatisfied need for a device and or method that reduces the time required to install a plurality of dambar punches in a dambar punch housing.
The invention provides a device, a dambar punch setup jig, which permits dambar punches to be rapidly installed in a dambar punch housing. The dambar punches are placed in the dambar punch setup jig, where their positions are fixed relative to one another. The dambar punches may be held in place on the dambar punch setup jig by a cover. Once installed in the dambar punch setup jig, the dambar punches can be simultaneously installed in a dambar punch housing. The dambar punch setup jig may then be removed, leaving the dambar punches installed in the dambar punch housing. The dambar punches are easier to install in the dambar punch setup jig then in the dambar punch housing, saving operator time. Using the jig substantially reduces the equipment downtime required to replace the dambar punches.
In one aspect, the invention provides a dambar punch setup jig including a body for holding a plurality of dambar punches, wherein the body is shaped so that dambar punches held by the body can be substantially installed in a dambar punch housing without releasing them from the body.
In another aspect, the invention provides a dambar punch setup jig including means for holding dambar punches and means for installing the held dambar punches in a dambar punch housing without releasing the dambar punches.
In a further aspect, the invention provides a method of installing a plurality of dambar punches in a dambar punch housing including the steps of placing the dambar punches in a module that holds the dambar punches, substantially installing the dambar punches in the dambar punch housing while the dambar punches are held by the module, and releasing the dambar punches from the module without de-installing the dambar punches from the dambar punch housing.
In a further aspect, the invention provides a method of removing a plurality of dambar punches from a dambar punch housing including the steps of installing a module around the dambar punches that holds the dambar punches and removing the module and dambar punches from the dambar punch housing as a unit.